Have you ever just wanted to be huge and destroy everything on your way? If so, Zac is your champion. He is insanely fun to play with his E and R combo. The thing I love about him, is that the more hp he has, the more it grows. With this guide you will have 5000 hp in the end, and you will still get a decent amount of kills. This is more of a support/tank guide rather then a full Ap, but trust me, it works better this way. So, lets begin!

P.S: my second guide, enjoy!

X3 Quint of ability power. X9 Marks of magic penetration. x9 Seals of health. X9 Glyphs of magic resist. You can change the seals with armor, but i wont recommend changing magic penetration marks into ability power marks.

As you have seen, we are not going to put even 1 single point into ferocity. The thing is, Zac has a huge amount of health a decent amount of damage. (137 AD/Level 18.) Plus, why would you have ferocity masteries when you are going tank? We are focusing on supporting, and taking all of the damage.

If you are engaging, your skill sequence would look something like this:
E > R > W > W > Q. By this time, if successful, you can pickup a kill or two.

Harassing in lane: Q > W > AA and repeat.

Stealing dragon: E > Q > flash

5 vs 5 team fight: E > R > W > W > Q > AA. This should make your team get some kills. Do not perform this if your team has few/no damage, it will simply make you waste your ult.

Skill sequence for what you need is above, but i will write it here too.
Q > E > W > Q > Q > R > Q > E > Q > E > R > E > W > E > W > R > W > W

PASSIVE: Cell Division
STATIC COOLDOWN: 300
Every time Zac damages at least one enemy with an ability, and for every enemy champion beyond the first hit by Elastic Slingshot, he sheds a chunk of himself to a nearby location which lands towards visible nearby enemy champions, if any, and lasts 6 seconds. Zac and enemies can move over these chunks to consume them, and if Zac does so he heals for 4% maximum health.
Upon taking fatal damage, Zac splits into 4 uncontrollable bloblets that move to his final location over 8 seconds. If any of these bloblets remain at the end of the duration, Zac recombines and returns at 10 - 50% maximum health, based on his bloblets' total remaining health.
Additionally, Zac's size scales with his health.

Q: Stretching Strike
RANGE: 550 COST: 4% CURRENT HEALTH COOLDOWN: 9 / 8.5 / 8 / 7.5 / 7
ACTIVE: Zac punches out in a line, dealing magic damage to all enemies he hits and Slow icon slowing them for 2 seconds.
MAGIC DAMAGE: 70 / 110 / 150 / 190 / 230 (+ 50% AP)
SLOW: 20 / 25 / 30 / 35 / 40%

W: Unstable Matter
RANGE: 350 COST: 4% CURRENT HEALTH COOLDOWN: 5
ACTIVE: Zac's body explodes outward, dealing magic damage to all nearby enemies, capped against minions and monsters. Zac also ignores unit collision against monsters damaged by Unstable Matter.
「 MAGIC DAMAGE: 40 / 55 / 70 / 85 / 100 (+ 4 / 5 / 6 / 7 / 8% (+ 2% per 100 AP) of target's maximum health) 」
Zac reduces Unstable Matter's cooldown by 1 second every time he picks up a chunk of Cell Cell Division. Picking them up while Unstable Matter is available instead reduces the cooldown of his next Unstable Matter by up to 1 second.

E: Elastic Slingshot
RANGE: 1200 / 1350 / 1500 / 1650 / 1800 / 300 COST: 4% CURRENT HEALTH COOLDOWN: 24 / 21 / 18 / 15 / 12
FIRST CAST: Zac channels for a short duration, increasing Elastic Slingshot's range over a cone in the target direction.
MAXIMUM CHANNEL DURATION: 0.9 / 1.05 / 1.2 / 1.35 / 1.5
If Zac moves during Elastic Slingshot, the ability is automatically cancelled, refunding half its cost and cooldown.
SECOND CAST: Zac dashes to the target location, dealing magic damage to all nearby enemies upon impact and Airborne icon knocking them up for 1 second.
MAGIC DAMAGE: 80 / 130 / 180 / 230 / 280 (+ 70% AP)

ULTIMATE: Let's Bounce!
RANGE: 300 / 400 COOLDOWN: 130 / 115 / 100
ACTIVE: Zac bounces 4 times and gains bonus movement speed as he does so, beginning at 20% and increasing to 50% over the duration, but also disables his ability to use basic attacks, Stretching Strike and Elastic Slingshot for the duration.
Each bounce deals magic damage to all nearby enemies, Airborne icon knocks them back for 1 second and subsequently Slow icon slows them by 20% for 1 second.
MAGIC DAMAGE PER BOUNCE: 140 / 210 / 280 (+ 40% AP)
Enemies can be damaged by multiple bounces, with each bounce beyond the first dealing half damage but applying no Airborne icon knock back.
「 ADDITIONAL MAGIC DAMAGE: 70 / 105 / 140 (+ 20% AP) 」

PROS CONS
A lot of CC
Very good in teamfights
A passive which makes him unkillable
Fun to play
Hard to carry if team is behind/has no damage
Hard to catch up if behind
Hard to master

For Zac, you will have to focus on getting as much health and armor/magic resist as possible. I have built 3 ways in 3 games, which are above. The third build is the best one because it has everything in it, from sustain to a great team player. For Zac you will also need to have some items which buffs your teammates, which in this case will be the locket of the solari.

You will always have to tank. ALWAYS. If you get a kill on the enemy top laner, or he is behind, go gank mid/bot. We want our whole team to snowball as much as they can. R has a lot of CC, which means E + R is a great engage.

Farming is not very hard with Zac. His Q + W combo makes farming somewhat easy, and makes it a good poke too. Don't rely on his W, without AP it's scaling is just awful and it does extremely low damage in the start.

Zac is super fun to play and very interesting. Every time you play with Zac, it feels great because you know exactly what to build and what to do. Zac is like Hulk, "ZAC IS ANGRY, ZAC SMAAAAAAAAAAAAAAASH!" I'll we'll be regularly updating this page, and make a guide on youtube on how to play him! Stay tuned for more!